Irukandji threat to southern waters

Researchers from Griffith University's Australian Rivers Institute have conducted a series of climate change simulation experiments to investigate whether the dangerous tropical jellyfish, the Irukandji, is likely to establish breeding populations in the South East.

It was found that while higher sea temperatures could provide an opportunity for adult Irukandji to expand their range south, increasing ocean acidification may inhibit the development of juveniles.

The research is the first step towards assessing if Irukandji pose a significant threat to tourism and human health in the South East. The findings have been published in the journal Global Change Biology.

Lead author, Griffith PhD student Shannon Klein said concerns have arisen from evidence world-wide that tropical marine species are moving towards the poles as oceans warm.

“Increasing ocean temperatures and strengthening boundary currents have caused the poleward migration of many marine species,” Shannon Klein said.

“These effects of climate change are particularly apparent on the eastern coast of Australia. Over the past 60 years the East Australian Current (EAC) has strengthened and now delivers warmer tropical waters further south by as much as 350km.”

As a consequence at least five species of tropical fish that occur on the Great Barrier Reef (GBR) are predicted to be able of survive winter temperatures in waters off Sydney by 2080. Among all species that could potentially expand their range south, the Irukandji would arguably have one of the greatest socio-economic impacts.

Irukandji have historically been limited to waters north of Gladstone, however in 2007 an adult specimen was recorded for the first time as far south as Hervey Bay.

“What we needed to find out was if the Irukandji would be able to establish their entire lifecycle south of their historical range in these expanded reaches of warm water or if adults only are able to drift south on the strengthened current,” Shannon said.

As it turns out the role of ocean acidification in limiting reproduction may hold the key to protecting the SE Queensland coastline. But we may not be out of hot water just yet.

“This response may reduce the likelihood of Irukandji jellyfish establishing permanent populations in South East Queensland in the long term, however, it is possible that they could migrate farther south in the short term if acidification proceeds slowly and appropriate reproduction habitats are available.

“But even if juvenile populations remain confined to more northerly waters there is still the strengthening EAC which could carry adults south.”

Irukandji jellyfish are represented by at least six species of cubozoan jellyfish which occur throughout the world's tropical zones, so the implications of this study are far reaching.

“Our results suggest that, if other Irukandji species behave similarly, range expansions could be occurring in other regions around the globe,” Shannon said.